For years, the wastes from burning coal and producing copper have enjoyed a second life, used in sand-blasting to remove paint, rust and grime from ship's hulls, storage tanks, bridge trusses and other surfaces. Painting contractors, shipyard workers and thousands of others in Baltimore and across the country are said to use the black, gritty material called slag.

Now, though, questions have been raised about whether those who do blasting with ground-up coal or copper slag may be unwittingly exposing themselves to toxic contaminants that could damage their health.

The Occupational Safety and Health Administration says coal and copper slag contain traces of highly toxic beryllium, arsenic and other contaminants. Federal regulators are investigating whether manufacturers of the blasting grit have provided adequate notice that users could be inhaling potentially harmful substances.

"When these abrasives are used in blasting, measured exposure levels to workers could exceed OSHA permissible exposure limits," OSHA spokesman Jesse Lawder said. Federal regulations require listing harmful substances in "material safety data sheets" which are supposed to alert employees to the risks involved with products they're dealing with in the workplace.

Area companies involved with the coal and copper slags said they follow federal rules in manufacturing and selling the material. And companies that use the slag to prepare surfaces for painting say their workers are protected with safety gear.

Officials with Opta Minerals Inc., a Canada-based company with a copper slag processing plant in East Baltimore, and for Harsco Corp., based in Camp Hill, Pa., said their slag-based blasting media, which are sold and used in shipyards and other businesses in the Baltimore area, are free of harmful levels of impurities. They said their companies have not been contacted by OSHA about why they don't list beryllium or other toxic contaminants in their product documentation.

Cary B. Lynch, vice president of General Ship Repair Corp. on Key Highway, said his shipyard has shifted to using mainly high-pressure water blasting to prepare ships' hulls for painting, but still uses copper slag to blast some steel surfaces.

"Our blasters use air-fed respirators when sand blasting," Lynch said. "All of the information we have seen shows the copper slag is not hazardous."

Arsenic and beryllium both occur naturally in soil and rocks, and they're found at low levels in the slag or waste products left over after burning coal or processing copper ore. Long-term or repeated exposure over years to the toxic inorganic form of arsenic has been linked to cancer of the bladder, lungs and other parts of the body. Beryllium is carcinogenic as well, but inhaling small amounts of the metal dust also can cause chronic beryllium disease, a pneumonia-like condition involving breathing difficulty, weakness and possible heart problems.

OSHA's statement pledging an investigation came after a public appeal last month from the nonprofit group Public Citizen, which contended that manufacturers of abrasives are violating federal rules requiring disclosure to workers of toxic chemicals in products they're working with.

Public Citizen's letter to OSHA said studies have shown that people working with coal-slag abrasives are exposed to levels of beryllium that far exceed OSHA safety limits. Justin Feldman, the group's worker health and safety advocate, said that while beryllium levels are lower in blasting with copper slag, tests show they are still twice OSHA's limit.

Adding to the group's concern is that the exposure limit set by OSHA is many times higher than what occupational health experts believe is safe. The American Conference of Governmental Industrial Hygienists, a professional group, recommends no more than 0.05 micrograms of beryllium per cubic meter of air workers are breathing, while OSHA's limit is 2 micrograms per cubic meter.

Health and labor groups have been pressing OSHA for more than a decade to reduce the safe workplace exposure limit to beryllium. Last fall, OSHA said deciding the issue was on its "long-term" agenda. The United Steelworkers union recently announced it had reached an agreement with beryllium products manufacturers to adhere to the industrial hygienists' recommended exposure limits and urged OSHA to lower the limit.

"In the absence of a protective standard for beryllium, we want to at least inform workers and employers who are using this substance that they are endangering people's lives," said Feldman. "Thousands get sick and die just from this coal slag."

A 2005 study for OSHA estimated that one-fourth of the 29,000 workers engaged in blasting work in shipyards and on construction sites are potentially exposed to beryllium. At the currently enforced exposure limit, the agency estimated anywhere from 120 to more than 600 workers each year could be getting beryllium disease, and one to two dozen contract cancer annually.

A spokesman for Harsco Corp. said in an email that the levels of beryllium and arsenic in the company's slag-based abrasives are no more than what's found in everyday soil.

"The fact is that all abrasives produced from natural sources are likely to contain trace amounts of metals and other elements," Harsco's Ken Julian said. The levels are so low they're not required to be listed on the product labels or on safety data sheets, he said.

Moreover, Julian said, the slag is "vitrified" or heat-hardened in processing so that any impurities are "encapsulated" or locked in the grains of blasting grit.

But Adam Finkel, a University of Pennsylvania law professor and former OSHA official who dealt for years with beryllium exposure issues, said testing has shown that when blasted via high-pressure nozzles against a surface, slag particles break down into dust, increasing the potential for exposure to contaminants.

Though workers are advised to wear air-fed respirators and protective clothing when doing blasting, Finkel said he'd seen cases of people with beryllium disease whose only exposure came from inhaling dust brought home from work by their spouses in their hair or on their clothes.

He credited Paul J. Mellon, president of Novetas Solutions in Philadelphia, which makes a competing blasting grit from recycled glass, with prodding OSHA to launch its investigation into whether slag-based hazards are properly disclosed.

"The sad part is that we really are talking about human health, not just workers but retail consumers," Mellon said.

Slag-based blasting grit is sold at building supply stores in the Baltimore area. A 50-pound bag of "Black Beauty," Harsco's brand name for its coal slag abrasive, bought for $9 at a local lumber store, does not mention arsenic, beryllium or any other contaminants on its label. The bag does advise anyone doing blasting, though, to wear protective gear, including an air-fed respirator, to avoid inhaling dust.

Fran Cohen, industrial hygienist at the Coast Guard's ship repair yard in Curtis Bay, said her facility also has shifted to blasting mainly with water, but does work with what she called "fused" coal slag that she said had been refined to remove contaminants. Blasting using slag is generally done inside a large booth to contain the dust, she said, and workers wear protective gear.

Cohen pointed out that many workplaces had shifted years ago to coal and copper slag for blasting, after it became clear that blasting with sand was exposing workers to harmful silica, which can also cause serious lung disease if inhaled.

Brian Burns, general manager for Opta's plants in Virginia and Maryland, said the company is retesting its slag-based products "to make sure we have good quality." If the results show contaminants at levels required to be disclosed, he said, they'll be listed.

The Baltimore plant at 4500 E. Fayette St. had processed coal slag until about a year ago, when the company shifted its stockpile to its Norfolk, Va., facility. Burns said the move was made after the Maryland Department of the Environment ordered the company to take steps to control rainfall runoff and windblown-dust from the coal slag it had stockpiled there. State regulations governing the handling and storage of coal-combustion waste byproducts require precautions to keep contaminants from seeping into ground water or nearby streams.

The Baltimore plant now processes copper slag shipped in from Japan, Burns said, which is sold under the brand name Ebonygrit. The black-looking slag is piled at the back of the company's lot, which is about two blocks from residences. Burns said the company complies with all state regulations.

"We do all the things we need to do to make sure it doesn't get out from our property to a stream or a neighbor," Burns said.

The OSHA spokesman said the agency is aware of "potential violations" involving manufacturers' failure to list the metals on the "material safety data sheets" accompanying the products, which are required under federal law to notify workers of potential hazards.

Lawder, declined to say what steps have been taken to investigate whether slag contaminants are properly disclosed, though in the statement he provided weeks ago he said it would be referred to the agency's field offices.

"It looks like they are doing the right thing," said Public Citizen's Feldman. But he pointed out that OSHA has had information for some time showing unsafe beryllium levels when blasting with slag.